Ion exchange modified with mercapto amines

ABSTRACT

This invention relates to a catalyst modified with mercapto amines, its preparation and its use for the preparation of bisphenols.

This application is a continuation of application Ser. No. 07/055,292,filed May 29, 1987, now abandoned.

The condensation of phenols and carbonyl compounds to produce bisphenolsis known. A wide variety of catalysts has already been used for thisreaction: for example, hydrochloric acid (U.S. Pat. Nos. 2,182,308 and2,191,831), boron trifluoride (Chemical Abstracts 58, 3338 c),perchloric acid (Chemical Abstracts 60, 1626 h), benzene sulphonic acid(Chemical Abstracts 59, 511 h) and various cation exchanger resins (e.g.GB-PS 842 209, 849 565 and 883 391). The addition of compoundscontaining sulphur to the catalyst is also known, e.g. the use ofthioglycollic acid and 3-mercaptopropionic acid has been disclosed inU.S. Pat. Nos. 2,468,982 and 2,623,908, the addition of thiophenols inU.S. Pat. Nos. 2,359,242, the addition of alkylmercaptans in U.S. Pat.Nos. 2,775,620 and the addition of hydrogen sulphide in ChemicalAbstracts 58, 1403 e.

These known catalysts containing sulphur give rise to considerabledamage by corrosion in industrial practice. Bisphenols prepared with theaid of these catalysts are contaminated crude products which containunreacted phenol, carbonyl compounds, water of reaction and undesirableby-products in addition to bisphenol. Bisphenol A synthesized with thesecatalysts, for example, contains isomers of bisphenol A, in particular2,2-(2,4'-dihydroxydiphenyl)-propane and2,2-(2,2'-dihydroxydiphenyl)-propane and complex products such as theso-called "codimer", 2,2,4-trimethyl-4-p-hydroxyphenylchroman,condensation products such as triphenol or even higher condensationproducts in the form of tarry or high boiling substances as well asdecomposition products and substances containing sulphur. The presenceof these by-products is undesirable as they tend to remain in the endproduct and give rise to discolouration. This impairs the usefulness ofthe end product even when a high degree of purity is not required. Inaddition, the by-products present interfere with some of the usualreactions of bisphenol, in particular its further reaction topolycarbonates.

U.S. Pat. No. 3,394,089 describes a process for the preparation ofbisphenol A from acetone and phenol with the aid of a catalystcontaining sulphonic acid groups in which 5 to 25 mols-% of thesulphonic acid groups are blocked with mercapto amines to form ammoniumsalts which are said to obviate these disadvantages. This modified ionexchanger resin which is obtained by neutralization in aqueous solution,for example with β-mercaptoethylamine, is unsuitable for the productionprocess because it is unstable and because the mercapto compound iswashed out by the reaction medium in the course of time so that thecatalyst loses its effect.

It has now been found that highly pure bisphenols may be prepared withthe aid of highly acid ion exchangers in which the acid groups areneutralized to a very high degree, even quantitatively, thisneutralization being carried out on a previously dried ion exchanger inan anhydrous medium.

The present invention relates to a process for the preparation ofanhydrous ion exchangers modified with mercapto amines, characterised inthat known acid ion exchanger resins which have a total capacity of acidfunctions of from 0.7 to 2.1 mval/ml of ion exchanger when they have awater content of about 75 to 85% by weight or a total capacity of acidfunctions of from 3.5 to 5 mval or higher, based on 1 g of dry substanceof ion exchanger, are dried and then rinsed with the phenol required forthe preparation of the bisphenol and are then neutralized with at least0.3 mol, preferably with 0.4 to 1 mol of mercapto amines of formula (I)per mol of acid function of the ion exchanger at temperatures above themelting point of this phenol.

The present invention also relates to the ion exchangers modified withmercapto amines of formula (I) obtainable by the process according tothe invention.

The acid functions of these modified ion exchangers are occupied withthe mercapto amine of formula (I) to an extent of at least 30 mol-% andpreferably 40 to 100 mol-%.

Suitable acid ion exchangers include, for example, the conventionalreaction products of styrene-divinyl benzene copolymers withconventional sulphonating agents such as sulphuric acid, chlorosulphonicacid etc. These may be present in spherical form with particle diametersof 0.3 to 1.5 mm. They may be of the gel type or macroporous. Theirtotal capacity of acid functions ranges from 0.7 to 2.1 mval/ml of ionexchanger when they are moistened with a water content of about 75 to85% by weight or from 3.5 to 5 mval or higher, based on 1 g of the drysubstance of ion exchanger.

Before the treatment or neutralization with the mercapto aminescorresponding to formula (I) which are to be used according to theinvention, these ion exchangers are dried, optionally by heat,optionally in a vacuum or optionally by washing with hydrophilic organicliquids such as alcohols or phenols or by azeotropic distillation withorganic liquids such as toluene, xylene, methylene chloride or others.The ion exchanger resin is then rinsed with the phenol required for thepreparation of the bisphenol, and the required quantity of mercaptoamine of formula (I) is then added in this medium at temperatures abovethe melting point of the phenol with stirring or in a fluidized bedlayer.

In the mercapto amines corresponding to formula (I) ##STR1## R¹ denotesa C₁ -C₆ -alkylene, C₅ -C₁₀ -cycloalkylene or C₆ -C₁₄ -arylene group,preferably a methylene group, and R² and R³, which are independent ofone another, denote C₁ -C₆ -alkyl groups or, preferably, hydrogen. Thefollowing are suitable mercapto amines corresponding to formula (I):Dimethylmercaptoethylamine, ethyl-cyclohexylmercaptobutylamine,mercaptopropylamine, 1-amino-4-mercaptomethylbenzene andβ-mercaptoethylamine: β-mercaptoethylamine is preferred.

The mercapto amines of formula (I) may be used as such or prepared insitu from thiazolidines such as 2,2-dimethyldiazolidine.

The cation exchanger resin which has been modified by neutralization maybe used for the preparation of numerous bisphenols from phenols andcarbonyl compounds. Suitable phenols include those corresponding toformula (II) ##STR2## wherein R¹, R², R³ and R⁴ denote, independently ofone another, hydrogen (H), C₁ -C₄ -alkyl or halogen such as F, Cl or Br.

The following are given as examples: 2,6-Dimethylphenol, o- andm-cresol, o-sec.butylphenol, o-tert.-butylphenol, 1,3,5-xylenol,2,6-ditert.-butylphenol, tetramethylphenol,2-methyl-6-tert.-butylphenol, o-phenylphenol, o- and m-chlorophenol,o-bromophenol, 6-chloro-o-cresol and 2,6-dichlorophenol.

Unsubstituted phenol is preferred.

Suitable carbonyl compounds include those corresponding to formula (III)##STR3## wherein R¹ and R² denote, independently of one another,hydrogen (H), C₁ -C₆ -alkyl, C₆ -C₁₀ -cycloalkyl, C₆ -C₁₄ -aryl, C₇ -C₂₀-aralkyl or C₇ -C₂₀ alkylaryl or R¹ and R² together form a saturatedring with 5 to 6 ring atoms.

The following are examples of suitable carbonyl compounds such asaldehydes and ketones: Formaldehyde, methyl ethyl ketone, methyl propylketone, diethyl ketone, cyclohexanone, acetophenone, etc. Acetone ispreferred.

The process of preparation may be carried out continuously or batchwiseby methods and with apparatus which are known in the art.

In the batchwise method, 80 to 200 g, preferably 100 to 150 g of drysubstance of ion exchanger resin according to the invention are used permol of carbonyl compound.

The reaction temperature employed for the preparation of the bisphenolis in the region of 40° to 120° C. and is preferably above thesolidification point of the components.

The reaction time or dwell time is chosen to be sufficiently long forcomplete conversion of the carbonyl compound put into the process and ispreferably from 30 to 240 minutes.

The present invention accordingly also relates to the use of the ionexchangers modified with mercapto amines of formula (I) obtained by theprocess according to the invention for the preparation of bisphenolsfrom phenols and carbonyl compounds.

The reaction mixture obtained from the reaction of phenol with carbonylcompound is worked up by the usual methods such as distillation,crystallisation, etc.

Thus, for example, the bisphenol prepared may be cooled in the reactionmixture until crystallisation sets in and the phenol may then be removedby distillation or extraction from the mixed crystals of bisphenol andphenol which have been filtered off.

The bisphenol prepared by this process is suitable for known fields ofapplication without after-purification and is also suitable forapplications in which an exceptionally high standard of purity isrequired, such as the preparation of optically highly purepolycarbonates.

EXAMPLE 1 Preparation of the Modified Ion Exchanger Resin

The water-moist ion exchanger as obtained from the supplier with amoisture content of about 80% by weight and a total capacity of 0.75mval/ml is washed with distilled water. It is then dried for 24 hours ina water jet vacuum at 90° to 100° C. to reduce the water content tobelow 1% by weight.

The remaining water is distilled off as an azeotropic mixture withtoluene and the toluene adhering to the ion exchange resin is thendistilled off in a water jet vacuum at 95° C.

120 g of this pretreated ion exchanger resin are taken up with 1128 g ofphenol in a stirrer apparatus and left to swell in the phenol at 65° C.for 24 hours with exclusion of moisture. The quantity of mercaptoethylamine required for blocking the mol-% indicated in Examples 2 to 10is then added with stirring.

EXAMPLES 2-10 Preparation of Bisphenol A (BPA)

The ion exchanger resin was modified with β-mercapto ethylamine by theprocess described in Example 1 so that 15 to 100% of the sulphonic acidgroups were neutralised in nine different adjustments. 58 g of acetonewere added at 65° C. to the solution prepared in Example 1 and thepurity of the bisphenol and quantity of by-products were determined gaschromatographically after complete conversion of the acetone. Theresults obtained are summarized in the following Table in terms of themean values obtained in each case from 5 experimental examples.

    ______________________________________                                                  Mol-%       GC surface percentages                                  Example   occupied    BPA    By-products                                      ______________________________________                                        2         15          93.6   6.4 (comparison)                                 3         20          93.8   6.2 (comparison)                                 4         25          94.3   5.7 (comparison)                                 5         30          94.5   5.5                                              6         40          94.7   5.3                                              7         50          95.1   4.9                                              8         60          95.7   4.3                                              9         80          96.2   3.8                                              10        100         96.7   3.3                                              ______________________________________                                    

We claim:
 1. A process for the preparation of anhydrous ion exchangersmodified with mercapto amines having improved stability in theproduction of bisphenols using acid ion exchanger resins having totalcapacities of acid functions of from 0.7 to 2.1 mval/ml of ion exchangerin the water-moist form with a water content of about 75 to 85% byweight or total capacities of acid functions of from 3.5 to 5 mval orhigher when based on 1 g of dry substance of ion exchanger, said processbeing characterized in that the resin is dried and thereafter rinsedwith the phenol required for preparation of the bisphenol and thereafterneutralized with at least 0.3 mol of mercapto amines corresponding toformula (I) per mol of acid function of the ion exchanger at atemperature above the melting point of bisphenol ##STR4## in whichformula (I), R¹ stands for C₁ -C₆ -alkylene, C₅ -C₁₀ -cycloalkylene orC₆ -C₁₄ -arylene and R² and R³ denote, independently of one another, C₁-C₆ -alkyl groups or hydrogen.
 2. Ion exchangers modified with mercaptoamines, obtainable according to claim
 1. 3. Process according to claim 1wherein the ion exchanger is neutralized with 0.4 to 1 mol of mercaptoamines per mol of acid function of the ion exchanger.
 4. Ion exchangersmodified with mercapto amines according to claim 2 which contain atleast 30 mol-% of neutralized mercapto amine.